Oliver Brown, 21, is accused of following Stephen Walsh, 37, back to his home before knocking him unconscious with a single blow causing a bleed on the brain.
Nottingham Crown Court heard his girlfriend Roseann Newton, 21, then tried to cover up the crime by blaming the injuries on the victim's fiance.
Mr Walsh's Lexus had collided with Mr Brown's Vauxhall Astra van in Mapperley, Nottingham, moments earlier on the night of July 29 last year.
But instead of stopping at the scene, Mr Walsh carried on home where he sat down to watch an episode of Love Island with his his fiancee Katie Brown, the jury was told.
Mr Brown then followed the builder home before he knocked on his door and attacked him on the doorstep, the court heard.
Mr Walsh was found dead at his home early the following morning and a post-mortem revealed he died as a result of head injuries.
Mr Brown, a glazing firm boss, of Ingoldmells, Lincs is accused of manslaughter.
Ms Newton, of Nottingham, is charged with assisting an offender and is accused of giving a false statement to police and deleting text messages.
Prosecutor Sarah Knight said the pair had come up with a "vicious lie" to try and blame Walsh's fiancee Katie Brown for his injuries.
Opening the case, she said Mr Walsh "was pronounced dead at the scene."
She added: "There was nothing that could be done to revive him. The Crown's case is that Stephen Walsh was unlawfully killed by Oliver Brown. Oliver's girlfriend, Roseann Newton tried to hide important evidence from police to try and protect Oliver Brown from being found out.
"On the last day that Mr Walsh was alive, Stephen Walsh and Katie Brown had attended a friend's christening.They stayed there until about 10.15pm. Mr Walsh was driving them home that evening in his Lexus. He had been drinking throughout the evening and should not have driven. Katie Brown was cross with him for doing this and had an argument with him at the time, but he insisted on driving them home.
"On their way home shortly after 10pm, Mr Walsh veered into the path of Oliver Brown, who was travelling with his girlfriend, Roseann Newton. Mr Brown was driving his Vauxhall Astra van. The two vehicles collided to a minor degree."
She said Mr Walsh should have stopped at the scene but had carried on home and "settled down to watch an episode of Love Island that they had recorded."
Mr Brown had driven round to try and track down the person who hit him, she said, adding that when Stephen Walsh answered the door "Oliver Brown remonstrated with him at the front door and then struck Mr Walsh hard to the face knocking him to the ground."
She added: "He was out cold and unconscious. The blow from Mr Brown and the impact caused by Mr Walsh's head falling to the ground resulted in fractures to his head and jaw. These led to a bleed on the brain that would tragically kill him just a few hours later."
A Home Office pathologist confirmed the cause of death to be underlying skull fracture and subdural haemorrhage. There were also areas of bruising to the left side of the neck, right ear and left upper jaw with an underlying fracture.
The court heard Brown handed himself into police on July 31 last year.
He denied being in an angry state when he set out to find Mr Walsh and claimed Mr Walsh had been drunk and aggressive.
Ms Newton was also spoken to by police, who also claimed Mr Walsh was aggressive and slurring his words when he answered the door.
Jurors were told she had deleted several messages to "keep evidence from the police."
The trial continues.